ACTG 382 is an open-label, AUC-controlled, multicenter study. All subjects will receive DMP 266 and nelfinavir. DMP 266 is a non-nucleoside reverse transcriptase inhibitor (NNRTI) which, in vitro, inhibits HIV production from infected cells. Dosage guidelines for children will be developed following analysis of the plasma level data and the DMP 266 dose used to obtain the target AUC. The primary objectives of the study are 1) to determine the dosing regimen of DMP 266 in combination with nelfinavir in children; and 2) to study the safety profile of DMP 266 in combination with nelfinavir in children.